When we started FLL seven years back, 2nd generation NXT was new and powerful and now the 3rd generation - EV3 has more powerful processor and storage choices. All legacy sensors should work and NXT platform still available till 2015. Both versions are allowed in 2013 season.
Take a first look at the three of the best EV3 - projects.
Want to know more about EV3 brick.
The EV3 is backward compatible. FLL and FTC related question fro NXT and EV3 cab be found in the Lego Education website.
Have fun reading.
Desh Deshmukh